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The cytokine interleukin (IL) 18 (formerly interferon [Gamma]-inducing factor) induces the T helper type 1 response. In the present studies, IL-18 increased HIV type 1 (HIV-1) production from 5- to 30-fold in the chronically infected U1 monocytic cell line. Inhibition of tumor necrosis factor (TNF) activity by the addition of TNF-binding protein reduced IL-18-stimulated HIV-1 production by 48%. In the same cultures, IL-18-induced IL-8 was inhibited by 96%. Also, a neutralizing anti-IL-6 mAb reduced IL-18-induced HIV-1 by 63%. Stimulation of UI cells with IL-18 resulted in increased production of IL-6, and exogenous IL-6 added to U1 cells increased HIV-1 production 4-fold over control. A specific inhibitor of the p38 mitogen-activated protein kinase reduced IL-18-induced HIV-I by 73%, and a 50% inhibition was observed at 0.05 [[micro]molar]. In the same cultures, IL-8 was inhibited by 87%. By gel-shift and supershift analyses, increased binding activity of the transcription factor NF-[Kappa]B was measured in nuclear extracts from UI cells 1 h after exposure to IL-18. These results demonstrate induction of HIV-1 by IL-18 in a monocyte target associated with an intermediate role for TNF and IL-6, activation of p38 mitogen-activated protein kinase, and nuclear translocation of NF-[Kappa]B.

The activator of the caspase cascade in vitro is investigated using caspase 9 (Casp9)-knockout mice. These mutant mice usually die at birth because of the failure of the cellular death machinery. The caspase cascade is an important component of cellular apoptosis without which cells continue to live and organ enlargement and malformation results. The addition of exogenous Casp9 induced the expression of the other caspase gene indicating that Casp9 is an upstream activator of the cascade.

The interleukin-1 β (IL-1β converting enzyme (ICE) processes the inactive IL-1 P precursor to the proinflammatory cytokine. Adherent monocytes from mice harboring a disrupted ICE gene ([ICE.sup.-/-] did not export IL-1β or interleukin-1α (IL-1α) after stimulation with lipopolysaccharide. Export of tumor necrosis factor-α and interleukin-6 (IL-6) from these cells was also diminished. Thymocytes from [ICE.sup.-/-] mice were sensitive to apoptosis induced by dexamethasone or ionizing radiation, but were resistant to apoptosis induced by Fas antibody, Despite this defect in apoptosis, [ICE.sup.-/-] mice proceed normally through development., The cytokine IL-1β plays a pivotal role in acute and chronic inflammation, bone resorption, myelogenous leukemia, and other pathological processes (1). IL-1β is synthesized as a 31-kD precursor devoid of [...]

Signal transduction via MAP kinase pathways plays a key role in a variety of cellular responses, including growth factor-induced proliferation, differentiation and cell death. In mammalian cells, p38 MAP kinase can be activated by multiple stimuli, such as pro-inflammatory cytokines and environmental stress. Although p38 MAP kinase is implicated in the control of inflammatory responses, the molecular mechanisms remain unclear. Upon activation, CD4+ T cells differentiate into Th2 cells, which potentiate the humoral immune response or pro-inflammatory Th1 cells. Here, we show that pyridinyl imidazole compounds (specific inhibitors of p38 MAPkinase) block the production of interferon-γ (IFNγ) by Th1 cells without affecting IL-4 production by Th2 cells. These drugs also inhibit transcription driven by the IFNγ promoter. In transgenic mice, inhibition of the p38MAPkinasepathwaybythe expression of dominant-negative p38MAPkinase results in selective impairment of Th1 responses. In contrast, activation of the p38MAP kinase pathway by the expression of constitutivelyactivatedMAPkinase kinase 6 in transgenic mice caused increased production of IFNγ during the differentiation and activation of Th1 cells. Together, these data demonstrate that the p38 MAP kinase is relevant for Th1 cells, not Th2 cells, and that inhibition of p38 MAP kinase represents a possible site of therapeutic intervention in diseases where a predominant Th1 immune response leads to a pathological outcome. Moreover, our study provides an additional mechanism by which the p38 MAP kinase pathway controls inflammatory responses. [ABSTRACT FROM AUTHOR]

The synthesis of novel, selective, orally active 2,5-disubstituted 6H-pyrimido[1,6-b]pyridazin-6-one p38α inhibitors is described. Application of structural information from enzyme-ligand complexes guided the selection of screening compounds, leading to the identification of a novel class of p38α inhibitors containing a previously unreported bicyclic heterocycle core. Advancing the SAR of this series led to the eventual discovery of 5-(2,6-dichlorophenyl)-2-(2,4-difluorophenylthio)-6H-pyrimido[1,6-b]pyridazin-6-one (VX-745). VX-745 displays excellent enzyme activity and selectivity, has a favorable pharmacokinetic profile, and demonstrates good in vivo activity in models of inflammation.